Iphone 根据NSURL请求的结果更新接口

我有一个应用程序，根据NSURL请求的结果更新界面。我将其设置为，当我的应用程序进入前台时，仅当当前视图控制器名为“ProfileViewController”时，才会触发请求

我的问题是，每次我从后台带回应用程序时，界面都会锁定几秒钟。我试图完全理解主线程/后台线程，但不确定在执行NSURL检查时如何使应用程序保持响应。任何帮助都会很好！谢谢

在我看来，加载方法：

-(void)viewDidLoad {

    [super viewDidLoad];

    [[NSNotificationCenter defaultCenter] addObserver:self
    selector:@selector(appReturnsActive) name:UIApplicationDidBecomeActiveNotification
    object:nil];

    //additional code
}

- (void)appReturnsActive {

    [myTimer invalidate];
    myTimer = nil;

    //ONLY WANT TO PERFORM THE UPDATE IF VIEWING THE PROFILE VIEW CONTROLLER
    UIViewController *currentVC = self.navigationController.visibleViewController;
    NSString * name = NSStringFromClass([currentVC class]);
    if ([name isEqualToString:@"ProfileViewController"]) { 

        [activityIndicator startAnimating];
        [activityIndicatorTwo startAnimating];
        locationManagerProfile.delegate = self;
        locationManagerProfile.desiredAccuracy = kCLLocationAccuracyBest;
        [locationManagerProfile startUpdatingLocation];    
    }
}

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation 
*)newLocation fromLocation:(CLLocation *)oldLocation {

    CLLocation *currentLocation = newLocation;
    if (currentLocation != nil) {

        [self performSelectorOnMainThread:@selector(buttonUpdate:)
        withObject:NULL waitUntilDone:NO];

    }
}

-(void)buttonUpdate {

NSString *userLongitude =[NSString stringWithFormat:@"%.8f", 
        currentLocation.coordinate.longitude];
        NSString *userLatitude = [NSString stringWithFormat:@"%.8f", 
        currentLocation.coordinate.latitude];
        [locationManagerProfile stopUpdatingLocation];
        NSString *placeLatitude = [[NSUserDefaults standardUserDefaults]
                                   stringForKey:@"savedLatitude"];
        NSString *placeLongitude = [[NSUserDefaults standardUserDefaults]
                                    stringForKey:@"savedLongitude"];
        NSString *distanceURL = [NSString 
        stringWithFormat:@"http://www.website.com/page.php?
        lat1=%@&lon1=%@&lat2=%@&lon2=%@",userLatitude, userLongitude, placeLatitude, 
        placeLongitude];

        NSData *distanceURLResult = [NSData dataWithContentsOfURL:[NSURL 
        URLWithString:distanceURL]];

        NSString *distanceInFeet = [[NSString alloc] initWithData:distanceURLResult 
        encoding:NSUTF8StringEncoding];

        if ([distanceInFeet isEqualToString:@"1"])
        {
            UIBarButtonItem *btnGo = [[UIBarButtonItem alloc] initWithTitle:@"Button 1" 
            style:UIBarButtonItemStyleBordered target:self 
            action:@selector(actionTwo)];
            self.navigationItem.rightBarButtonItem = btnGo;

            UIBarButtonItem *btnGoTwo = [[UIBarButtonItem alloc] initWithTitle:@"Button 
            Two" style:UIBarButtonItemStyleBordered target:self 
            action:@selector(actionOne)];
            self.navigationItem.rightBarButtonItem = btnGoTwo;

            self.navigationItem.rightBarButtonItems = [NSArray arrayWithObjects:btnGo, 
            btnGoTwo, nil];
        }
}

然后在我的应用程序中返回活动方法：

-(void)viewDidLoad {

    [super viewDidLoad];

    [[NSNotificationCenter defaultCenter] addObserver:self
    selector:@selector(appReturnsActive) name:UIApplicationDidBecomeActiveNotification
    object:nil];

    //additional code
}

- (void)appReturnsActive {

    [myTimer invalidate];
    myTimer = nil;

    //ONLY WANT TO PERFORM THE UPDATE IF VIEWING THE PROFILE VIEW CONTROLLER
    UIViewController *currentVC = self.navigationController.visibleViewController;
    NSString * name = NSStringFromClass([currentVC class]);
    if ([name isEqualToString:@"ProfileViewController"]) { 

        [activityIndicator startAnimating];
        [activityIndicatorTwo startAnimating];
        locationManagerProfile.delegate = self;
        locationManagerProfile.desiredAccuracy = kCLLocationAccuracyBest;
        [locationManagerProfile startUpdatingLocation];    
    }
}

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation 
*)newLocation fromLocation:(CLLocation *)oldLocation {

    CLLocation *currentLocation = newLocation;
    if (currentLocation != nil) {

        [self performSelectorOnMainThread:@selector(buttonUpdate:)
        withObject:NULL waitUntilDone:NO];

    }
}

-(void)buttonUpdate {

NSString *userLongitude =[NSString stringWithFormat:@"%.8f", 
        currentLocation.coordinate.longitude];
        NSString *userLatitude = [NSString stringWithFormat:@"%.8f", 
        currentLocation.coordinate.latitude];
        [locationManagerProfile stopUpdatingLocation];
        NSString *placeLatitude = [[NSUserDefaults standardUserDefaults]
                                   stringForKey:@"savedLatitude"];
        NSString *placeLongitude = [[NSUserDefaults standardUserDefaults]
                                    stringForKey:@"savedLongitude"];
        NSString *distanceURL = [NSString 
        stringWithFormat:@"http://www.website.com/page.php?
        lat1=%@&lon1=%@&lat2=%@&lon2=%@",userLatitude, userLongitude, placeLatitude, 
        placeLongitude];

        NSData *distanceURLResult = [NSData dataWithContentsOfURL:[NSURL 
        URLWithString:distanceURL]];

        NSString *distanceInFeet = [[NSString alloc] initWithData:distanceURLResult 
        encoding:NSUTF8StringEncoding];

        if ([distanceInFeet isEqualToString:@"1"])
        {
            UIBarButtonItem *btnGo = [[UIBarButtonItem alloc] initWithTitle:@"Button 1" 
            style:UIBarButtonItemStyleBordered target:self 
            action:@selector(actionTwo)];
            self.navigationItem.rightBarButtonItem = btnGo;

            UIBarButtonItem *btnGoTwo = [[UIBarButtonItem alloc] initWithTitle:@"Button 
            Two" style:UIBarButtonItemStyleBordered target:self 
            action:@selector(actionOne)];
            self.navigationItem.rightBarButtonItem = btnGoTwo;

            self.navigationItem.rightBarButtonItems = [NSArray arrayWithObjects:btnGo, 
            btnGoTwo, nil];
        }
}

最后，在我的Did-Update-Location方法中，我得到了用户和位置之间的距离。如果结果等于1，则更新界面以显示不同的按钮。这就是界面冻结的地方：

-(void)viewDidLoad {

    [super viewDidLoad];

    [[NSNotificationCenter defaultCenter] addObserver:self
    selector:@selector(appReturnsActive) name:UIApplicationDidBecomeActiveNotification
    object:nil];

    //additional code
}

- (void)appReturnsActive {

    [myTimer invalidate];
    myTimer = nil;

    //ONLY WANT TO PERFORM THE UPDATE IF VIEWING THE PROFILE VIEW CONTROLLER
    UIViewController *currentVC = self.navigationController.visibleViewController;
    NSString * name = NSStringFromClass([currentVC class]);
    if ([name isEqualToString:@"ProfileViewController"]) { 

        [activityIndicator startAnimating];
        [activityIndicatorTwo startAnimating];
        locationManagerProfile.delegate = self;
        locationManagerProfile.desiredAccuracy = kCLLocationAccuracyBest;
        [locationManagerProfile startUpdatingLocation];    
    }
}

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation 
*)newLocation fromLocation:(CLLocation *)oldLocation {

    CLLocation *currentLocation = newLocation;
    if (currentLocation != nil) {

        [self performSelectorOnMainThread:@selector(buttonUpdate:)
        withObject:NULL waitUntilDone:NO];

    }
}

-(void)buttonUpdate {

NSString *userLongitude =[NSString stringWithFormat:@"%.8f", 
        currentLocation.coordinate.longitude];
        NSString *userLatitude = [NSString stringWithFormat:@"%.8f", 
        currentLocation.coordinate.latitude];
        [locationManagerProfile stopUpdatingLocation];
        NSString *placeLatitude = [[NSUserDefaults standardUserDefaults]
                                   stringForKey:@"savedLatitude"];
        NSString *placeLongitude = [[NSUserDefaults standardUserDefaults]
                                    stringForKey:@"savedLongitude"];
        NSString *distanceURL = [NSString 
        stringWithFormat:@"http://www.website.com/page.php?
        lat1=%@&lon1=%@&lat2=%@&lon2=%@",userLatitude, userLongitude, placeLatitude, 
        placeLongitude];

        NSData *distanceURLResult = [NSData dataWithContentsOfURL:[NSURL 
        URLWithString:distanceURL]];

        NSString *distanceInFeet = [[NSString alloc] initWithData:distanceURLResult 
        encoding:NSUTF8StringEncoding];

        if ([distanceInFeet isEqualToString:@"1"])
        {
            UIBarButtonItem *btnGo = [[UIBarButtonItem alloc] initWithTitle:@"Button 1" 
            style:UIBarButtonItemStyleBordered target:self 
            action:@selector(actionTwo)];
            self.navigationItem.rightBarButtonItem = btnGo;

            UIBarButtonItem *btnGoTwo = [[UIBarButtonItem alloc] initWithTitle:@"Button 
            Two" style:UIBarButtonItemStyleBordered target:self 
            action:@selector(actionOne)];
            self.navigationItem.rightBarButtonItem = btnGoTwo;

            self.navigationItem.rightBarButtonItems = [NSArray arrayWithObjects:btnGo, 
            btnGoTwo, nil];
        }
}

新方法：

-(void)viewDidLoad {

    [super viewDidLoad];

    [[NSNotificationCenter defaultCenter] addObserver:self
    selector:@selector(appReturnsActive) name:UIApplicationDidBecomeActiveNotification
    object:nil];

    //additional code
}

- (void)appReturnsActive {

    [myTimer invalidate];
    myTimer = nil;

    //ONLY WANT TO PERFORM THE UPDATE IF VIEWING THE PROFILE VIEW CONTROLLER
    UIViewController *currentVC = self.navigationController.visibleViewController;
    NSString * name = NSStringFromClass([currentVC class]);
    if ([name isEqualToString:@"ProfileViewController"]) { 

        [activityIndicator startAnimating];
        [activityIndicatorTwo startAnimating];
        locationManagerProfile.delegate = self;
        locationManagerProfile.desiredAccuracy = kCLLocationAccuracyBest;
        [locationManagerProfile startUpdatingLocation];    
    }
}

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation 
*)newLocation fromLocation:(CLLocation *)oldLocation {

    CLLocation *currentLocation = newLocation;
    if (currentLocation != nil) {

        [self performSelectorOnMainThread:@selector(buttonUpdate:)
        withObject:NULL waitUntilDone:NO];

    }
}

-(void)buttonUpdate {

NSString *userLongitude =[NSString stringWithFormat:@"%.8f", 
        currentLocation.coordinate.longitude];
        NSString *userLatitude = [NSString stringWithFormat:@"%.8f", 
        currentLocation.coordinate.latitude];
        [locationManagerProfile stopUpdatingLocation];
        NSString *placeLatitude = [[NSUserDefaults standardUserDefaults]
                                   stringForKey:@"savedLatitude"];
        NSString *placeLongitude = [[NSUserDefaults standardUserDefaults]
                                    stringForKey:@"savedLongitude"];
        NSString *distanceURL = [NSString 
        stringWithFormat:@"http://www.website.com/page.php?
        lat1=%@&lon1=%@&lat2=%@&lon2=%@",userLatitude, userLongitude, placeLatitude, 
        placeLongitude];

        NSData *distanceURLResult = [NSData dataWithContentsOfURL:[NSURL 
        URLWithString:distanceURL]];

        NSString *distanceInFeet = [[NSString alloc] initWithData:distanceURLResult 
        encoding:NSUTF8StringEncoding];

        if ([distanceInFeet isEqualToString:@"1"])
        {
            UIBarButtonItem *btnGo = [[UIBarButtonItem alloc] initWithTitle:@"Button 1" 
            style:UIBarButtonItemStyleBordered target:self 
            action:@selector(actionTwo)];
            self.navigationItem.rightBarButtonItem = btnGo;

            UIBarButtonItem *btnGoTwo = [[UIBarButtonItem alloc] initWithTitle:@"Button 
            Two" style:UIBarButtonItemStyleBordered target:self 
            action:@selector(actionOne)];
            self.navigationItem.rightBarButtonItem = btnGoTwo;

            self.navigationItem.rightBarButtonItems = [NSArray arrayWithObjects:btnGo, 
            btnGoTwo, nil];
        }
}

---

您的CoreLocation委托方法（例如“

didUpdateToLocation

”等）都发生在后台的次线程上

要解决问题，您应该在主线程上修改UI。你可以使用的一个简单的基础API是：

要解决您的问题，请将创建代码的按钮移动到一个单独的方法中，并从旧方法（通过CoreLocation委托协议在单独的线程上调用）通过“

performSelectorOnMainThread

”调用该新方法，这样您就可以开始了

NSData *distanceURLResult = [NSData dataWithContentsOfURL:[NSURL 
    URLWithString:distanceURL]];

---

是一个同步呼叫。这意味着您的代码将等待网络调用的结果继续。您应该使用NSURLConnection（）或AFNetworking发出异步请求。

感谢您的响应！！！我是否应该将didUpdateLocation方法中的所有内容都放在即将创建的新方法中？我假设我会把几乎所有的东西都放在if（currentLocation！=nil）行下面。在我自己的代码中，如果我需要从后台线程中修改主线程上的UI，我会在单独的线程上尽可能多地做，以保持用户界面（和用户体验）尽可能精神饱满。似乎在工作！！一个相关的小问题。当我在新方法中包含包含currentLocation.coordinate.longitude的NSString时，我得到一个错误，我可以修复它吗？当然，您可以修复它。其中一个参数是“

withObject

”。为什么不把那串东西传过去？哇。太明显了。你太棒了！事实上，我需要更新我的问题并发布我到目前为止的代码，因为无论我做了什么，我的应用程序都会崩溃。好的，迈克尔，刚刚更新过。有什么想法吗？非常感谢。